In the manufacture of mass-produced products a production line may involve the sequential assembly of parts using a large number of welding stations. At each welding station there may be a welding tool having first and second electrodes. Welding electrodes are generally made of copper. However, the substrate material need not be limited to copper. For example, coatings of vanadium-carbide, tungsten-carbide, titanium-diboride, zirconium-diboride, Titanium-carbide, Cr3C2, and so on, might be applied to various tool steels or aluminum, or other metals, as may be. The end of the electrode generally carries a cap, which may have a size and shape suitable for making the desired weld. The cap is also typically made of copper or a copper alloy, and may be hollow. The tip of the cap will have a size and shape suitable for the objects to be welded. The welding, work-piece contacting, contact end of the cap may, at least initially, be substantially spherical, or it may have the shape of a truncated cone, or it may have some other shape. At the tip of the cap there may be a coating of some kind, be it titanium carbide or titanium di-boride, or some other coating, such as may tend to delay deterioration of the cap.
It may be helpful to have a tool for aiding in the coating of the cap. In the electro-spark deposition process, a consumable piece of electrode material is brought into contact with a metallic base surface to be treated. The surface area will be coated with a layer of the electrode material when swept by the electrode. The electrode cap may be mounted to a moving device. The condition of the contacts is dependent on the relative motion of the rod of depositing electrode coating material and the electrode cap to be coated.